This invention particularly relates to an ecofriendly process for the preparation of acyl heteroaromatic compounds from heteroaromatic compounds using acid anhydrides as acylating agents and metal exchanged clays as catalysts dispensing the use of stoichiometric amounts of corrosive, toxic aluminium chloride and other Lewis and protic acids as Friedel-Crafts reagents. The acylated products are valuable intermediates for drugs, pharmaceuticals, flavours and fragrances.
2-acetylthiophene is normally prepared by Friedel-Crafts acetylation of thiophene with acetic acid, acetyl chloride or acetic anhydride in the presence of a Lewis acid or a proton acid. The product is purified by distillation and it regularly contains from 1-2% of 3-acetyl thiophene as an impurity. For most purposes 2 -acetylthiophene of 98-99% is adequate.